We’re now at the point where every single analyst is releasing sales estimates for Apple (AAPL) devices ahead of the company’s quarterly earnings report, and AppleInsider points us to a new note from J.P. Morgan analyst Mark Moskowitz claiming that relatively low iPad sales could hurt Apple’s bottom line far more than iPhone 5 sales. According to Moskowitz, supply constraints could limit iPad sales over the holiday quarter to 18.4 million units, down from the 20.1 million units that he’d previously forecasted. Moskowitz says that such a miss would be “explainable” because it would be caused by “a supply — not demand — issue.”

Moskowitz also projects that Apple will report strong iPhone sales of nearly 48 million units for the holiday quarter, which could assuage some investor disappointment at relatively lackluster iPad sales.

All the same, J.P. Morgan has lowered its 12-month price target on Apple shares to $725, down from an earlier target of $770. As we mentioned earlier, though, we’ve seen a wide range of contradictory reports on Apple’s holiday quarter sales and we won’t know for certain how well or poorly the company did until it releases its results next week.